Increased mortality in patients with standard EEG findings of 'diffuse slowing'.

Background: We aimed to confirm the association between slow brain wave activity typically described as "diffuse slowing" on standard electroencephalogram (EEG) and patient outcomes, including mortality.

Methods: This retrospective study was conducted with patient chart data from March 2015 to March 2017 at a tertiary care academic hospital in the midwestern United States. In total, 1,069 participants age ≥55 years on an inpatient floor or ICU received a standard 24-hour EEG. The primary outcome was all-cause mortality at 30, 90, 180, and 365 days. Secondary outcomes were time to discharge, and discharge to home.

Results: Having diffuse slowing on standard EEG was significantly associated with 30-, 90-, 180-, and 365-day mortality compared with patients who had normal EEG findings, after controlling for age, sex, and Charlson Comorbidity Index score. When controlling for these factors, patients with diffuse slowing had a significant longer time to discharge and were significantly less likely to discharge to home. Our findings showed that a standard EEG finding of diffuse slowing for inpatients age ≥55 years is associated with poor outcomes, including greater mortality.

Conclusions: This study suggested that the finding of diffuse slowing on EEG may be an important clinical marker for predicting mortality in geriatric inpatients.